For writing to discs multiple times you have two options:

  • Multi-Session (Nero: ☑Allow files to be added later)
  • UDF (Windows 7 and later: Live File System)

What are the differences, Pros and Cons?


Universal Disk Format (UDF) is described on Wikipedia as:

Universal Disk Format (UDF) is a profile of the specification known as ISO/IEC 13346 and ECMA-167[5] and is an open vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660. Due to its design, it is very well suited to incremental updates on both recordable and (re)writable optical media.

Multi-session has always been part of the UDF specification (UDF 2.01/6.10.1), though some implementations may be unable to read disks with multiple sessions or will only read the last session.

Each session has its own complete data tables, which wastes space. I have heard 20 megabytes mentioned as the overhead per each additional session. Multiple session CD-R discs were first implemented by Kodak to allow CD-R disks to be written to until the CD is full. As with the traditional CD-R, you cannot erase data once written to the disc, but the same disc can be used until it is full, each session modifying (adding or replacing) files from the previous sessions.


First thing first: A session is a recorded segment that may contain one or more tracks of any type. The optical disc recorder doesn’t have to write the entire session at once. you can write a single track, and come back later and write another but the session must be “closed” before a standard disc player will be able to use it. Additional sessions can be added until the optical disc is closed or there’s no space left. This provides a simple and fairly reliable way to write some data to a disc now and still be able to add more later.

Multisession is a technique which allows data be added incrementally in more than one recording, allowing you to add, update, or delete files and directories. All the data on a multisession disc can be seen as if it were all recorded at the same time (if you linked the data between sessions)

Universal Disk Format (UDF), a configuration file known as ISO/IEC 13346 and ECMA-167, is an open supplier-neutral file system. It is used to save computer data of various media. In practice, UDF is most widely used in DVD and updated disk formats replacing ISO 9660.

So multisession is a technique to record data segment on optical discs, while UDF is a vendor-neutral file system for computer data storage for a broad range of media, optical disc include.

As far I ubderstand you can't make comparison between them, because you are using both in the same task.

In my own experience, multisession have the advantage of flexibility on the disc data store capacity, the con is that in every iteration of use your chance of disc corruption increase. UDF got in favour that is almost everywhere, the cons are that has a very limited pathname length, in comparison with latest technologies and got some restrictions in some OS denpending on UDF version.

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